Roller hearth furnace with roll oscillation controller

ABSTRACT

A ROLLER HEARTH FURNACE INCLUDES A FURNACE SECTION FOR HEATING WORK ARTICLES AND AN EXIT SECTION ADJACENT THE FURNACE SECTION FOR RECEIVING HEATED ARTICLES FROM THE FURNACE SECTION. THE ARTICLES ARE SUPPORTED BY A PLURALITY OF SPACED PARALLEL ROTATABLE ROLLS WITH THE ROLLS IN THE FURNACE SECTION BEING ROTATED BY A REVERSIBLE ELECTRIC MOTOR. A ROLL OSCILLATION CONTROLLER IS PROVIDED FOR AUTOMATICALLY REVERSING THE DIRECTION OF ROTATION OF THE MOTOR EACH TIME ONE OF THE ROLLS ROTATES THROUGH A COMPLETE REVOLUTION TO THEREBY OSCILLATE THE ROLLS FOR OSCILLATING ARTICLES BACK AND FORTH IN THE FURNACE SECTION. MEANS ARE PROVIDED FOR OPERATING THE OSCILLATION CONTROLLER EITHER MANUALLY OR AUTOMATICALLY, THE AUTOMATIC OPERATION BEING IN RESPONSE TO ARRIVAL OF AN ARTICLE AT A POSITION IN THE FURNACE SECTION NEAR ITS EXIT END WHILE AN ARTICLE IS POSITIONED IN THE EXIT SECTION SO AS TO PREVENT A JAM OF ARTICLES.

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Filed May 22, 1970 Sept. y20, 197:1?` r. F. PRICE ETAL ROLLER HEARTH FURNACE WITH ROLL OSCILLATION CONTROLLER Filed may 22, 1970 4 Sheets-Sheet 4 ANW INVENTORS TALMADGE'. F. PRICE.

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ROBERT R.wA| ToN Bv @W ATTORNEY j`United States Patent 3,606,281 ROLLER HEARTH FURNACE WITH ROLL OSCILLATION CONTROLLER Talmadge F. Price and Robert R. Walton, Shelbyville, Ind., assignors to General Electric Company Filed May 22, 1970, Ser. No. 39,725 Int. Cl. B271) 4/14 U.S. Cl. 26S-6C 17 Claims ABSTRACT OF THE DISCLOSURE A roller hearth furnace includes a furnace section for heating Work articles and an exit section adjacent the furnace section for receiving heated articles from the furnace section. The articles are supported by a plurality of spaced parallel rotatable rolls with the rolls in the furnace section being rotated by a reversible electric motor. A roll oscillation controller is provided for automatically reversing the direction of rotation of the motor each time one of the rolls rotates through a complete revolution to thereby oscillate the rolls for oscillating articles back and forth in the furnace section. Means are provided for operating the oscillation controller either manually or automatically, the automatic operation being in response to arrival of an article at a position in the furnace section near its exit end while an article is positioned in the exit section so as to prevent a jam of articles.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to roller hearth furnaces, and more particularly to such a furnace including a roll oscillation controller for controlling oscillation of work articles back and forth Within the furnace section.

Description of the prior art In roller hearth furnace installations it may be desirable at times to oscillate work articles back and forth within the furnace section. For example, such oscillation of Work articles is very desirable to prevent a chain reaction jam of such articles in the event article handling equipment at the exit section is for some reason not prepared to remove articles from the exit section as they leave the furnace section. One prior art method for oscillating work articles within the furnace section utilizes a timer which is arranged to effect reversal of the main motor drive for the rolls periodically in accord with a preset timing period. However, such method has the disadvantage that when the main motor drive changes speed due to different article loading conditions on the rolls, the distance through which the articles oscillate will also change for a constant timer setting. Such change in oscillation distance is undesirable and in order to avoid it, an operator must change the timer setting each time a different load is received by the furnace. This is a tiresome and time consuming procedure and frequently the operator will forget to change the timer setting. Further, insofar as is known, the prior art has made no provision for automatically effecting oscillation of work articles in the furnace section in response to arrival of an article at a position in the furnace section near its exit end while an article is positioned in the exit section so as to prevent a jam of articles. It has been the practice when a jam of articles occurs, to stop the main motor for terminating rotation of the rolls. However, this is undersirable inasmuch as the rolls would sag due to loading and high temperatures.

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OBJECTS 0F THE INVENTION It is an object of the invention to provide a roller hearth furnace including a novel and improved roll oscillation controller for controlling oscillation of work articles within the furnace section.

It is another object of the invention to provide a roller hearth furnace including a novel and improved roll oscillation controller for effecting oscillation of work articles within the furnace section automatically in response to arrival of an article at a position in the furnace section near its exit end While an article is positioned in the exit section.

It is still another object of the invention to provide a furnace as defined in the preceding object wherein oscillation of the articles is automatically terminated when the articles are oscillated to their original position occupied prior to the beginning of oscillation after removal of the article from the exit section.

It is a further object of the invention to provide a roller hearth furnace including a novel and improved roll oscillation controller for effecting oscillation of work articles within the furnace section through a substantially constant distance in each direction regardless of variations in the speed of the motor which drives the rolls supporting the articles.

It is a still further object of the invention to provide a furnace as defined in thevpreceding object wherein the direction of rotation of the rolls is automatically reversed each time the rolls rotate through substantially a complete revolution.

SUMMARY OF THE INVENTION In carrying out the invention in one preferred form a roller hearth furnace is provided including a furnace section for heating work articles and an exit section adjacent the furnace section for receiving heated articles from the furnace section. The furnace includes a plurality of spaced parallel rotatable rolls for supporting the articles and drive means is provided for rotating the rolls about their axes to convey the articles through the furnace section to the exit section. The drive means includes a reversible electric motor which when rotated in one direction effects rotation of the rolls in the furnace section in one direction and which when rotated in the opposite direction effects rotation of the rolls int he furnace section in the opposite direction. A roll oscillation controller is provided which is effective when operated to reverse the direction of rotation of the motor each time one of the rolls rotates through approximately a complete revolution to thereby oscillate the rolls for oscillating articles back and forth in the furnace section.

The oscillation controller may be placed into operation either manually or automatically and when automatic operation is desired, sensing means is employed for operating the oscillation controller automatically in response to arrival of an article at a position in the furnace section near its exit end while an article is positioned in the eXit section. The articles in the furnace section are thereby oscillated back and forth for preventing their conveyance to the exit section so long as an article remains inthe exit section. The oscillation controller includes switch means actuatable to a first position for effecting rotation of the motor in one direction and actuatable to a second position for effecting rotation of the motor in the opposite direction. A switch actuator is arranged for selective connection to one of the rolls for rotation therewith to actuate the switch means to its first and second positions in alternation each time said one roll rotates substantially a complete revolution. Connection of the switch actuator to said one roll is controlled by an electric clutch which in turn is controlled by manually operated means or by theaforementioned automatic sensing means las desired.

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings described below.

BRIEF DESCRIPTION OF THE DRAWINGSy FIG. 1 is a view in top plan of a roller hearth furnace including a roll oscillation controller in accord with the present invention;

FIG. 2 is a view in side elevation of the roller hearth furnace of FIG. l showing work articles in positions effective to initiate automatic operation of the oscillation controller;

FIG. 3 is a view in side elevation of the switch means and switch actuator employed in the oscillation controller showing the actuator in its normal position prior to operation of the controller;

FIG. 4 is a View similar to FIG. 3 showing the actuator displaced in a clockwise direction from its position in FIG. 3 to a position wherein the actuator actuates the switch means after the controller has been set in operation;

FIG. 5 is a View similar to FIG. 2 showing the work articles in the furnace section displaced toward the left from their positions in FIG. 2 to positions occupied after completion of one half of a full oscillation;

FIG. 6 is a view similar to FIG. 4 showing the actuator displaced approximately 360 in a counterclockwise direction from its position in FIG. 4 to a position wherein the actuator actuates the switch means after completion of one half of a full oscillation;

FIG. 7 is a View similar to FIG. 5 showing the work articles in the furnace section displaced toward the right from their positions in FIG. 5 to positions occupied after completion of one or more full oscillations and effective to terminate operation of the controller;

FIG. 8 is a view similar to FIG. 6 showing the actuator displaced in a clockwise direction from its position in FIG. 6 to its position after completion of one or more full oscillations;

FIG. 9 is a circuit diagram showing control circuits employed in the roller hearth furnace of FIG. 1; and

FIG. l() is a view in perspective with parts shown in section illustrating the switch actuator and the switch means shown in FIGS. 3, 4, 6 and 8, and also illustrating an electric clutch employed to control connection of the actuator to one of the rolls.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings there is illustrated in FIGS. 1 and 2 a roller hearth furnace incorporating the improved oscillation controller of the present invention. The roller hearth furnace comprises an elongated horizontally extending structure including a first loading or entrance section 12, a second intermediate heating or furnace section 14 and a third unloading or exit section 15. As shown in FIGS. 1 and 2 these three sections 12, 14 and 15 are horizontally aligned and the entrance section 12 is adapted to reecive work articles 17 (FIG. 2) which are to be heated and which are transferred from the entrance section 12 through the furnace section 14 to the exit section 15 in the manner described hereinafter. The articles 17 may for example comprise slabs of material to be heated or may comprise trays containing material to be heated. In FIG. 2 one article 17 is shown in the entrance section 13, four articles 17 are shown in the furnace section 14 and one article 17 is shown in the exit section 15.

The entrance section 12 and the exit section 1S are open and accessible so as to facilitate loading and unloading of articles 17 relative to the furnace, such loading and unloading being accomplished in any suitable manner such as automatically or manually as desired. The

furnace section 14 includes a horizontally extending top Wall 18 and a pair of spaced parallel upstanding side walls 20 to substantially enclose the furnace section. A pair of doors D1 and D2 are provided each at a separate end of the furnace section 14, the doors D1 and D2 depending from adjacent the ends of the top wall 18 and extending transversely of the furnace substantially the full width thereof. The doors D1 and D2 are movable in generally vertical directions as viewed in FIG. 2 between closed positions shown in FIG. 2 and open positions wherein the doors are elevated above the top wall 18 to open the ends of the furnace section 14. In order to control opening and closing movements of the doors D1 and D2, suitable control means are provided including reversible motors DOM1 and DOM2 each having up and down windings UP and DO (FIG. 9), such door control means being more fully described hereinafter. Heat is supplied to the furnace section 14 in any suitable manner, such as by electric heating elements or gas fired burners (not shown) suitably arranged in the furnace section 14.

In order to support the articles 17 and to permit their translation through the furnace section 14, a plurality of spaced parallel rotatable rolls 21 (FIG. l) are provided in each of three sections 12, 14 and 15. The rolls 21 are spaced in the direction of elongation of the furnace and the axes of the rolls extend generally perpendicular to the direction of elongation of the furnace. As shown in FIG. l, the rolls 21 in the entrance section 12 have their ends respectively journaled in bearings 22 carried by spaced side frames 24. In like manner, the rolls 21 in the furnace section 14 have their ends journaled in bearings 25 carried by the side walls 20, and the rolls 21 in the exit section 15 have their ends journaled in bearings 26 carried by spaced side frames 27. In the embodiment illustrated, there are ve rolls 21 in the entrance section 12, fteen rolls 21 in the furnace section 14, and four rolls 21 in the exit section 15.

In order to eifect rotation of the rolls 21 about their axes, drive means are provided which may assume any suitable form. In the preferred embodiment illustrated in FIGS. 1 and 2, the drive means includes a plurality of sprockets 29 each rotatable with a separate one of the rolls 21, the sprockets 29 being xedly mounted on the ends of shafts 30 secured to the rolls 21. The four sprockets 29 associated with the first four rolls 21 in the entrance section 12 are interconnected by a link chain 31, and the sprocket 29 associated with the iifth roll 21 in the entrance section 12 and the four sprockets 29 associated with the rst four rolls 21 in the furnace section 14 are interconnected by a link chain 32. A pair of additional sprockets 34 and 36 are carried by the shafts 30 secured to the fourth and fifth rolls 21 in the entrance section 12, the sprockets 34 and 36 being interconnected by a link chain 38 which 1s driven `by a first drive motor 39. A clutch EC1 is associated with the sprocket 36 for controlling connection thereof to the associated shaft 30. The clutch lECl is pref- .erably an electric clutch having an energizable coil which 1s elfective when energized to connect the sprocket 36 to the associated shaft 30 for rotation therewith, the sprocket 36 being disconnected from the associated shaft 30 when the coil of clutch ECI is deenergized.

Continuing further with the description of the drive means, a pair of additional sprockets 42 and 43 are carried by the shaft 30 secured to the fourth and fth rolls 21 in the furnace section 14. The sprockets 42 and 43 are interconnected by a link chain 44 and an electric clutch EC2 having an energizable coil is .associated with the sprocket 42 for controlling connection thereof to the associated shaft 30. The seven sprockets 29 which are associated with the fifth, sixth, seventh, eighth, ninth, tenth and eleventh rolls 21 in the furnace section 14 are interconnected by a link chain 46 which is driven by a main electric drive motor 48. The motor 48 is a reversible motor having forward yand reverse windings (FIG. 9) so as to permit rotation of the rolls 21 in the furnace section 14 in opposite directions. A pair of additional sprockets 49 and 50 are carried by the shafts 30 secured to the eleventh and twelfth rolls 21 in the furnace section 14, the sprockets 49 and 50 being interconnected by a link chain 51. An electric clutch ECS having an energizable coil is associated with the sprocket 50 for controlling connection thereof to the associated shaft 30. The sprockets 29 associated with the last four rolls 21 in the furnace section 14 and the first roll 21 in the exit section 15 are interconnected by a link chain 53. A pair of additional sprockets 54 and 55 are carried by the shafts 30 secured to the first and second rolls 21 in the exit section 15 and are interconnected by a link chain 56 which is driven by a motor 57. An electric clutch EC4 having an energizable coil is associated with the sprocket 54 for controlling connection thereof to the associated shaft 30. A link chain 60 interconnects the sprockets 29 associated with the last three rolls 21 in the exit section 15.

In order to effect certain controlling functions a plurality of limit switches are provided for actuation in response to travel-of the articles 17 along the three sections 12, 14 and 15 of the roller hearth furnace. For this purpose normally open limit switches FLSl, FLSZ, FLS3 and FLS4 are provided as shown in FIG. 1, these limit switches being actuated respectively to closed conditions in response to pivotal movement of suitable actuating flags F1, F2, F3 and F4 spaced along the length of the furnace in the path of travel of the articles 17. As best shown in FIG. 2, the flag F1 is positioned between the fourth and fifth rolls 21 in the entrance section 12, the flag F2 is positioned between the fourth and fifth rolls 21 in the furnace section 14, the flag F3 is positioned between the fourteenth and fifteenth rolls 21 in the furnace section 14, and the flag F4 is positioned beyond the last roll in the exit section 15. When the flags F1, F2, F3 and F4 are engaged and pivoted in a clockwise direction by articles 17, the associated limit switches are actuated to closed conditions. The flags F1, F2, F3 and F4 are spring biased to their normal vertical positions so that when an article 17 has passed over a flag, the flag returns to its normal position. The limit switches FLSl, FLS2, FLS3 and FLS4 also are spring biased so as to return to their normal open conditions when the associated flags return to their normal positions. In certain installations the high temperatures produced in the furnace may prohibit the use of flag operated limit switches and in such installations photoelectric controlled switches may be employed instead of flag operated limit switches.

In order to effect certain additional controlling functions a plurality of other limit switches are arranged for actuation in response to opening and closing movements of the doors D1 and D2. As shown in FIG. 2, limit switches DSDl, GCS1 and DSU1 are disposed for actuation by an actuator 62 which is movable in vertical directions in accord with movement of the door D1, and limit switches DSD2, GCS2 and DSU2 are disposed for actuation by an actuator 63 movable in vertical directions in accord with movement of the door D2. The limit switches DSD1, GCS1, DSD2 and GCS2 are normally open when the doors D1 and D2 are closed and are actuated closed when the doors D1 and D2 are opened. The limit switch DSU1 includes a pair of switches DSUlA and DSUlB (FIG. 9) which are respectively closed and open when the door D1 is closed and which are actuated open and closed when the door D1 is opened. Similarly, the limit switch DSU2 includes a pair of switches DSUZA and DSU2B which are respectively closed and open when the door D2 is closed and which are actuated open and closed when the door D2 is opened.

It may be desirable at times to oscillate articles 17 back and forth within the furnace section 14. For example, such oscillation of articles 17 within the furnace section 14 is very desirable to prevent a chain reaction jam of such articles in the event article handling equipment at the exit section 15 is for some reason incapable of removing articles from the exit section as they leave the furnace section. In accord with the invention a novel and improved oscillation controller is provided for effecting oscillation of articles 17 within the furnace section 14. Such oscillation controller is effective when operated to reverse the direction of rotation of the main drive motor 48 automatically in response to predetermined angular rotation of one of the rolls 21. The oscillation controller preferably operates to reverse the direction of the motor 48 each time one of the rolls 21 rotates through approximately a complete revolution. The oscillation controller may be placed into operation either manually or automatically and when automatic operation is employed, the oscillation controller is operated in response to arrival of an article 17 at a position within the furnace section 14 adjacent the door D2 while an article 17 is in the exit section 15. With such arrangement articles 17 within the furnace section 14 are oscillated back and forth for preventing their conveyance to the exit section 15 so long as an article 17 remains in the exit section whereby a jam of such articles is prevented.

In accord with the preferred embodiment of the invention, the oscillation controller includes switch means 65 shown in FIGS. 3, 4, 6, 8 and 10 actuatable to arfirst position for effecting rotation of the motor 48 in one direction and actuatable to a second position for effecting rotation of the motor 48 in the opposite direction. The switch means 65 is actuatable by an actuator 66 which is arranged for selective connection to one roll 21A (FIG. l) of the rolls 21 for rotation therewith to actuate the switch means 65 to its first and second positions in alternation each time the roll 21A rotates through substantially a complete revolution. The roll 21A associated with the actuator 66 may comprise any one of the rolls 21 which are interconnected by the chain 416 driven by the motor 48. An electric clutch 67 is provided for controlling connection of the actuator 66 to the roll 21A. More specifically, with reference to the particular embodiment shown in FIG. l0 the switch means 65 comprises a housing 68 which pivotally supports an operating lever 69 which is spring biased to a normally vertical neutral position and which is mounted for pivotal movement in opposite directions from the neutral position. The lever 69 is effective when pivoted from its neutral position to operate a pair of normally open switches 70 and 71 within the housing 68 and shown in the circuit diagram of FIG. 9. 'I'he lever 69 is in the path of rotation of the actuator 66 to be pivoted thereby. As will presently appear, the switch 70 is closed in response to clockwise rotation of the actuator 66 as viewed in FIG. 3 to effect rotation of the motor 48 in one direction for rotating the rolls 21 in a counterclockwise direction as viewed in FIG. 2, and the switch 71 is closed in response to counterclockwise rotation of the actuator 66 to effect rotation of the motor 48 in the opposite direction for rotating the rolls 21 in a clockwise direction.

With reference to FIG. 10 the clutch l67 is shown as including a cylindrical hub 73 having an axial keyway 74 adapted to receive a key (not shown) formed on the shaft 30 which is secured to the roll 21A so as to fix the l hub 73 to the roll 21A for rotation therewith. The hub 73 includes an annular flange 75 which is located between an annular magnetic stator 76 and an annular magnetic armature 77 which is attached to the actuator 66 by screws 78. The actuator 66 is preferably in the form of a pointer and extends generally perpendicular to the axis of the hub 73, the hub 73 projecting through an opening of the actuator 66. The stator 76 is fixed to the furnace structure in any suitable manner and is in the form of an annular cup surrounding the hub 73 with the open side of the cup facing the flange 75. The armature 77 is in the form of a solid ring which surrounds the hub 73 and an annular spacer 80 surrounds the hub 73 between the armature 77 and flange 75, the spacer 80 being fixed to the armature 77 by the screws 78. In order to permit rotation of the hub 73 relative to the stator 76, a bearing race 81 containing ball bearings 82 is positioned between the hub 73 and stator 76. A pair of additional axially spaced bearing races 84 containing ball bearings 8S are located between the armature 77 and the hub 73 to permit rotation of the hub 73 relative to the armature 77 when the clutch 67 is deenergized. The clutch 67 includes a coil 86 adapted for energization in accord with direct current to create magnetic flux for magnetically fixing the armature 77 relative to the hub 73. As shown in FIG. the coil `86 is wound in the form of a toroid and is positioned within the cup of the stator 76 to surround the hub 73. The coil 86 is connected across output terminals 87 (FIG. 9) of a full wave bridge rectifier 88 having input terminals 89 connected to a suitable source of alternating voltage represented by power conductors L1 and L2 shown in FIG 9. When the coil 86 is in a deenergized condition, the hub 73 rotates relative to the armature 77 and the actuator 66 attached thereto. For such condition the actuator 66 depends substantially vertically to bear against the right side of a roller 69 on the lever 69 primarily due to a counterweight 90 attached to the lower end of the actuator 66.

In order to effect various controlling functions a plurality of relays are provided as shown in FIG. 9. Each of these relays has energizable coil means and one or more sets of contacts responsive to the condition of energization of the associated coil means. In the following decription contacts of the various relays are designated by the reference character used to identify the relay followed by a numerical identification. The designations normally open (NO) or normally closed (NC) as applied in respect to contacts of the relays refer to the conditions of the contacts when the associated coil means are deenergized. In FIG. 9 all contacts are shown in their normally open or normally closed conditions,

In the circuit of FIG. 9 there are a total of twelve relays as follows. A first main relay IMR includes first NO contacts 1MR1 in the energizing circuit for the up winding UP of door motor DOM1, second NO contacts 1MR2 in the energizing circuit for the down winding DO of door motor DOM1, and third NO contacts 1MR3 in the energizing circuit for the motor 39. A first control relay 1CR includes rst NO contacts 1CR1 in the energizing circuit for the coil of clutch ECl, second NO contacts 1CR2 in the energizing circuit for the motor 39, third NC contacts 1CR3 in the energizing circuit for the coil of clutch ECZ, and fourth NC contacts 1CR4 in the energizing circuit for the coil of a timing relay 1TR. A second control relay ZCR includes first NO contacts 2CR1 in the energizing circuit for the down winding DO of door motor DOM1, second NC contacts 2CR2 in the energiz ing circuit for the motor 39, and third NC contacts 2CR3 in series with the contacts 1CR4. The timing relay 1TR is provided to assure proper spacing of the articles 17 as they progress along the furnace and include NO time delayed contacts 1TR1 in the energizing circuit for the up winding of motor DOM1, and NO contacts lTRZ in parallel with contacts 2CR3. The timing relay lTR is arranged so that it starts timing when its coil is energized and the contacts 1TR1 will close after elapse of a preselected time subsequent to energization of the coil of relay 1TR. An alarm relay ALR includes first NC contacts ALR1 in the energizing circuit for a first alarm device, such as a horn H, and second NO contacts ALRZ in an energizing circuit for a second alarm device, such as a lamp LA. The series connection of the contacts ALR1 and the horn H is in parallel with the series connection of the contacts ALR2 and the lamp LA.

Further, a relay 10R includes first NC contacts 10R1 in the energizing circuit for the up winding of motor DOM1, second NO contacts 10R2 in series with the parallel combination of contacts ALR1 and horn H and contacts ALRZ and lamp LA, third NO contacts 10R3 in an energizing circuit for the coil of relay 10R, fourth NOVcontacts 10R4 in the energizing circuit for the latch coil L of a latch type relay 1LR, fifth NO contacts 10R5 in the energizing circuit forrthe unlatch coil U of relay 1LR, and sixth NO contacts 10R6 in the energizing circuit for the coil of clutch 67. Thev latch type relay 1LR includes NC contacts 1LR1 in the energizing circuit for the forward winding F of the main drive motor 48, and NO contacts 1LR2 in the energizing circuit for the reverse Winding R of the main drive motor 48. When both coils of the latch type relay 1LR are deenergized, the contacts 1LR1 are closed and the contacts 1LR2 are open. When the unlatch coil U is energized, the contacts 1LR1 are open and the contacts 1LR2 are closed and the contacts remain in such conditions after the unlatch coil is deenergized. When the latch coil is energized, the contacts 1LR1 are closed and the contacts 1LR2 are open and remain so when the latch coil is deenergized.

In addition, a second main relay 2MR includes first NO contacts 2MR1 in the energizing circuit for the up winding UP of door motor DOM2, second NO contacts ZMRZ in the energizing circuit for the down winding DO of door motor DOM2, and third NO contacts 2MR3 in the energizing circuit for the motor 57. A control relay 6CR includes first NO contacts 6CR1 in series with NO contacts 1OR3 of Vrelay 1OR and second NO contacts 6CR2 in the energizing circuit for the up winding UP of door motor DOM2. A control relay SCR includes first NO contacts 3CR1 in an energizing circuit for the coil of relay 1OR and second NO contacts 3CR2 in the energizing circuit for the up 9 Winding UP of door motor DOM2. A control relay 4CR includes first NO contacts 4CR1 in series with the contacts 3CR1, second NC contacts 4CR2 in the energizing circuit for the up winding UP of door motor DOM2, third N0 contacts 4CR3 in the energizing circuit for the down winding of door motor DOM2, and fourth NC contacts 4CR4 in the energizing circuit for the motor 57. Finally, a control relay SCR includes first NC contacts 5CR1 in the energizing circuit for the coil of clutch EC3 and second NO contacts SCRZ in the energizing circuit for the coil of clutch EC4.

The limit switch FLS1 and the switch DSUIA are in series in the energizing circuit for the up winding UP of door motor DOMl and the limit switch FLSZ is in the energizing circuit for the coil of relay ZCR. Further, the limit switches FLS3 and FLS4 are in the energizing circuits for the coils of relays 3CR and 4CR respectively. Also, the switch DSUIB is in the energizing circuit for the coil of relay 1CR, and the limit switch DSD1 is in the energizing circuit for the down winding DO of door motor DOM1. The switch DSUZA is in the energizing circuit for the coil of relay GCR, and the switch DSUZB is common to the energizing circuits for the motor 57 and the coil of relay SCR. The limit switch DSD2 is in the energizing circuit for the down winding DO of door motor DOM2. A "manual-automatic switch 92 is in the energizing circuit for the coil of relay 1MR, a manualautomatic switch 93 is in the energizing circuit for the coil of relay ZMR, an off-on switch 94 is in the energizing circuit for the forward and reverse windings of the motor 48, and a "normal-oscillation switch 95 is in a third energizing circuit for the coil of relay 10R.

Operation of the yfurnace and the roll oscillation controller will now be described. With reference to FIG. 9 let it be assumed that there are no articles 17 in the furnace and that therefore the limit switches FLS1, FLSZ, FLSS and FLS4 are open. Assume further that the manualautomatic switches 92 and 93 are actuated to their lower automatic positions, so that the coils of relays 1MR and ZMR are energized, that the off-on switch 94 is actuated to its lower on position, and that the normaloscillation switch 95 is actuated to its upper normal position so as to permit automatic operation of the oscillation controller as will presently appear. For these conditions the door D1 is closed since the limit switch FLSI is open so that the up winding UP of motor DOM1 is deenergized. Further, since the limit switch FLS3 is open, the coil of relay 3CR is deenergized whereby its NO contacts 3CR2 are open so that the up winding UP of motor DOM2 is deenergized andthe door D2 is also closed. l

. With the door D1 closed, the switch DSUlB is open whereby the coil of relay 1CR is deenergized and its NO contacts 1CR1 and 1CR2 are open so that both the coil of clutch ECI and the motor 39 are deenergzed whereby the first four rolls 21 in the entrance section 12 are not rotating. However, NC contacts 1CR3 are closed so that the coil of clutch EC2 is energized and since both switches 70 and 71 are open the latch coil L and the unlatch coil U of relay ILR are both deenergized whereby contacts 1LR1 are closed and contacts 1LR2 are open so that the "forward and reverse windings of motor 48 are respectively energized and deenergized. In addition, NC contacts 1CR4 are closed and since switch FLS2 is open, the coil of relay 2CR is deenergized -so that NC contacts 2CR3 are closed whereby the coil of timing relay 1TR is energized. This results in instantaneous closure of contacts 1TR2 and closure of contacts 1TR1 after elapse of a preselected time subsequent to energization of the coil of relay 1TR. Further, with door D2 closed, the switch DSU2B is open whereby both the motor S7 andthe coil of relay SCR are deenergized. Therefore, NC contacts SCRl are'closed so that the coil of clutch ECS is energized and NO contacts 5CR2 are open so that the coil of clutch EC4 is deenergized. Accordingly, the fifth roll 21 in the entrance section 12, all rolls 21 in the furnace section 14, and the first roll in the exit section are rotating in a clockwise direction as viewed in FIG. 2, and the last three rolls 21 in the exit section 15 are not rotat' ing. The furnace is now prepared to receive articles 17 in the entrance section 12. v An article 17, such as a tray containing material to be heated, s placed in the entrance section 12 and is pushed forward (toward the right as viewed in FIG. 2) until it actuates flag F1 to close switch FLSl. Assuming that contracts 1TR1 are closed by this time, closure of switch FLSI results in energization of up winding of motor DOM1 through now closed contacts 10R1, 1TR1 and 10 DSUIA, and opening of switches GCS1 and DSD1. Openf ing of switch DSUlB deenergizes the coil of relay ICR which opens contacts 1CR1 to deenergize. the coil of clutch ECI, opens contacts ICR2 to deenergize the motor 39, closes contacts 1CR3 to energize the coil of clutch EC2, and closes contacts 1CR4 which has no effect since contacts 2CR3 are open at this time. Closure of switch DSUIA has no effect since time delayed .contacts 1TR1 are open at this time. Openingof switch GCS1 closes the valve VLV1 to terminate the gas curtain and opening of switch DSD1 effects deenergization of the down 1MR1 and switch DSUlA. This results in raising of the door D1 and lowering of the actuator 612 which sequentially closes switchesV DSD1 and GCS1, opens switch DSUlA and closes switch DSUlB. Closure of switch DSD1 has no effect since contacts 2CR1 are open at this time. Closure of switch GCS1 opens a Valve VLV1 to applya gas curtain adjacent the open door D1. Opening of switch DSUlA deenergizes the up winding of motor DOM1 to thereby stop opening movement of the door D1. Closure of switch DSUIB energizes the coil of relay 1CR which closes contacts 1CR1 and 1CR2 and opens contacts 1CR3 and 1CR4 to thereby energize both the coil of clutch EC1` and motor 39 and vdeenergize both the coil of clutch EC2 and the coil of timing relay 1TR. This results in rotation of the tiverolls 21 in the entrance section 12 and the first four rolls in the furnace section 14 in a clockwise direction for moving the article 17 from the entrance -sectionthrough the open door D1 and into the furnace section at a preselected speed under control of motor 39. Moreover, deenergization of the coil of timing relay 1TR resets this relay vso that `bothcontacts 1TR1 and contacts 1TR2 open.`

As the article 17 enters the furnace section, it actuates flag-F2 which closes switch FLS2 to energize the coil of relay ZCR. This results in closure of contacts 2CR1 to etect energization of the down winding of motor DIM1 through now closed contact-s 1MR2 and switch DSD1,

opening ofvcontacts 2CR2 to deenergizemotor 39; and

winding of vmotor DOM1. The rst article 17 is accordlngly conveyed along the furnace section at a preselected speed under control of the motor 48. As the trst article 1711sso conveyed, it passes over the flag F2 whereby the switch FLS2 opens to deenergize the coil of relay 2CR. This closes contacts 2CR3 to effect energization of the coil of timing relay 1TR through now closed contacts 1CR4. Energization of the coil of timing relay 1TR results in instantaneous closure of its contacts 1TR2 and closure of contacts 1TR1 after elapse of the timing period which effects energization of the up winding of motor DOM1 1f a second article is engaging ag F1 in the entrance section such that the switch FLSl is closed. At this time the sequence above described for the first article 17 is repeated for the second article 17.

The first article 17 is conveyed along the furnace section until it actuates flag F3 which closes switch F183 to energize relay 3CR. This causes closure of contacts 3CR1 which has no effect since contacts 4CR1 are open at this time, and closure of contacts 3CR2 for effecting energization of the up winding of motor DOM2 through now closed contacts 4CR2, 2MR1 and 6CR2 to open the door D2. Opening of the door D2 lowers the actuator 63 which sequentially closes switches DSD2 and GCS2, opens switch DSU2A and closes switch DSU2B. Closure of switch DSD2 has no effect since contacts 4CR3 are open at this time. Closure of switch GCS2 opens valve VLV2 to apply a gas curtain adjacent the open door D2. Opening of switch DSUZA deenergizes the coil of relay 6CR to open contacts 6CR1 which has no eiect since contacts 1OR3 are open at this time, and to open contacts 6CR2 for deenergizing the up winding of motor DOM2 to terminate opening movement of door D2. Closure of switch DSU2B energizes the motor 57 through now closed contacts 4CR4 and 2MR3 and energizes the coil of relay SCR which opens contacts 5CR1 to deenergize the coil of clutch EC3 and closes contacts 5CR2 to energize the coil of clutch EC4. This results in rotation of the last four rolls 21 in the furnace section and the four rolls 21 in the exit section to move the first article 17 from the furnace section through the open door D2 to the exit section at a preselected speed under control of motor 57.

As the rst article 17 enters the exit section, it actuates flag F4 which closes switch FLS4 to energize the coil of relay 4CR. This results in closure of contacts 4CR1 which has no eifect since the second article 17 has not yet advanced to a position for actuating the flag F3 so that contacts 3CR1 are open at this time, opening of contacts 4CR2 which has no effect since contacts 3CR2 and 6CR2 are open at this time, closure of contacts 4CR3 which energizes the down winding of motor DOM2 through now closed contacts 2MR2 and switch DSD2, and opening of contacts 4CR4 to deenergize motor 57. The door D2 is thereby closed and resulting elevation of actuator 63 causes sequential opening of switch DSU2B, closing of switch DSUZA, and opening of switches GCS2 and DSD2. Opening of switch DSU2B deenergizes the coil of relay SCR which closes contacts 5CR1 to energize the coil of clutch EC3 and opens contacts 5CR2 to deenergize the coil of clutch EC4. Closing of switch DSUZA energizes the coil of relay GCR to close contacts 6CR1 which has no effect since contacts 1OR3 are open at this time, and to close contacts 6CR2 which has no effect since both contacts 3CR2 and 4CR2 are open at this time. Opening of swith GCS2 terminates the gas curtain and opening of switch DSD2 deenergizes the down winding of motor DOM2. The first article 17 should now be removed from the exit section so that the exit section will be cleared to receive the second article 17 from the furnace section. If the iirst article is removed from the exit section to release ag F4 prior to actuation of flag F3 by the second article, then the second article will be transferred to the exit section as described above in connection with the first article.

Let it be assumed that for some reason the rst article is not removed from the exit section in timely fashion and that it still actuates the flag F4 When the second article arrives at the ag F3 and actuates it. If the normal sequence of operation described above were permitted to continue under such conditions, the door D2 would open and the second article would be conveyed to the exit section whereupon it would collide with the rst article thus causing a chain reaction jam of articles along the furnace, assuming additional articles were following along. In accord with the invention such a jam up of articles is prevented by automatically placing the roll oscillation controller into operation when both limit switches FLS3 and FLS4 are in closed conditions simultaneously. When both switches FLS3 and FLS4 are closed, the coils of relays 3CR and 4CR are energized so that contacts 3CR1 and 4CR1 are closed to energize the coil of relay 10R. 'Ihis results in opening of contacts 1OR1 to prevent opening of the door D1 in the usual manner if an article is engaging flag F1 in the entrance section, closing of contacts 1OR2 which energizes the horn H through now closed contacts ALR1, closure of contacts 1OR3 which maintains energization of the coil of relay 1OR when the coil of relay SCR is deenergized in response to opening of switch FLS3 by release of flag F3 during oscillation of the second article within the furnace section, closure of contacts 1OR4 t0 permit energization of the latch coil of relay 1LR each time switch 71 is closed during oscillation, closure of contacts 1ORS to permit energization of the unlatch coil of relay 1LR each time switch 70 is closed during oscillation, and closure of contacts 1OR6 to energize the coil of clutch 67.

When the clutch 67 is energized, the actuator 66 is connected to the roll 21A and rotates therewith in the clockwise direction from the position shown in FIG. 3 to the position shown in FIG. 4 wherein it pivots the lever 69 which closes switch 70. Closure of switch 70 energizes the unlatch coil of relay 1LR which opens contacts 1LR1 and closes contacts 1LR2 to thereby respectively deenergize and energize the forward and reverse windings of motor 48. This causes a reversal in the direction of rotation of motor 48 whereby the rolls 21 are rotated in counterclockwise directions to move the articles 17 in the furnace section toward the left as viewed in FIG. 2. At the same time, the actuator 66 is rotating with the roll 21A in the counterclockwise direction from its position shown in FIG. 4 and when the lever 69 is released it returns to its neutral position and the switch 70 opens. Opening of switch 70 deenergizes the unlatch coil of relay 1LR which is ineffective to change the conditions of contacts 1LR1 and 1LR2. When the roll 21A and the actuator 66 complete a full revolution in the counterclockwise direction, the actuator 66 pivots the lever 69 towards the right as viewed in FIG. `6 to close the switch 71 to energize the latch coil of relay 1LR. This closes contacts 1LR1 and opens contacts 1LR2 to reverse the direction of rotation of the motor 48 a second time which reverses the direction of rotation of the rolls 21 a second time. Such second reversal occurs after substantially a complete revolution of the rolls 21 so that just prior to the second reversal the articles 21 in the furnace section are in the positions shown in FIG. displaced to the left from their positions shown in FIG. 2 by a distance equal approximately to the circumference of a roll.

The second reversal effects movement of the articles toward the right from their positions shown in FIG. 5. During this time the actuator 66 is rotating with the roll 21A from its position shown in FIG. 6 in a clockwise direction and when it reaches the position shown in FIG. 8, the articles have been moved to positions shown in FIG. l7 which are the same positions occupied by the articles as shown in FIG. 2 when roll oscillation was initiated. Thus, a complete cycle of roll oscillation has ybeen completed and if at this time the rst article still remains in the exit section of the flag F4, roll oscillation-will continue.

It will be recalled that the horn H is energized at the beginning of roll oscillation to alert the operator that the article in the exit section was not removed as it should have been. Having been so alerted by sounding of the horn H the operator actuates the spring return pushbutton switch PB to its lower position as' viewed in FIG. 9 to thereby energize the lamp LA and the coil of relay ALR through now closed contacts 1OR2 which opens vcontacts ALR1 to deenergize the horn H and closes contacts ALR2 to maintain energization of the coil of relay ALR and the lamp LA after the switch PB is released. The lamp LA will remain energized until relay 1OR is deenergized and contacts 1OR2 are opened at the termination of roll oscillation.

Assume now that the operator removes the first article 17 from the exit section. Such removal releases the tlag F4 which opens switch FLS`4 to deenergize the coil of relay 4CR. This results in opening contacts 4CR1 which is ineffective to deenergize the coil of relay 1OR whose energization is maintained through closed contacts 10'R3 and 6CR1, closing contacts 4CR2 to prepare the up winding of motor DOM2. for energization in response to closure of contacts 3CR2, opening contacts 4CR3 which has no effect since switch DSD2 is'open, and closing contacts 4CR4 which has no effect since switch DSUZB is open. Inasmuch as the coil of relay 1OR is still energized, roll oscillation will continue until such time as the second article returns to its original position after one or more full cycles of oscillation and actuates ag F3 to close switch FLS3. This energizes the coil of relay SCR to close contacts 3CR1 which has no eifect since contacts 10R3 .and 6CR1\ are both closed, and to close contacts 3CR2 which effects energization of` up winding of motor DOM2l to open door D2. The opening movement of door D2 opens switch DSUQA to deenergize the coil of relay 6CR, and closes switch DSUZB to energize both the motor I57 and the coil of relay SCR. When the coil of relay 6CR is deenergized contacts 6CR1 open to deenergize the coil of relay 1OR and contacts 6CR2open to deenergize the up winding of motor DOM2. Energization of the coil of relay SCR results in opening of contacts 5CR1 to deenergize the coil of clutch ECS and closure of contacts 5CR2 to energize the coil of clutch EC4 so that the second article is moved to the exit section. When the coil of relay 10K is deenergized in response to opening of` switch DSUZA, its several contacts return to their normal conditions with the result that the coil of 4clutch 67 is deenergized to disconnect the actuator 66 from the roll 21A to terminate the oscillation operation.

There are occasions when it may be desired to place the controller into operation manually rather than automatically as described above even though the exit section is clear of vfan article. Such manual operation may for example be desired to test operation of the controller or to subject articles within the furnace section to further heat treatment. In order to elfect manual operation of the controller the switch is actuated to its lower position in FIG. 9 wherein it shunts the series connected contacts 3CR1 and 4CR1 and also the series connected contacts 10R3 and 6CR1 in parallel with the contacts 3CR1 and 4CR1. Such actuation of the switch 95 effects energization of the coil of relay IGR to initiate operation of the oscillation controller in the manner previously described.

13 Operation of the controller is terminated by actuating the switch 95 to its upper position shown in FIG. 9.

The roll oscillation controller of the present invention possesses many advantages. First, it provides a completely automatic arrangement for preventing a jam'of articles in the event an article is for some reason not removed from the exit'section. Second, the controller operates to oscillate the rolls through a complete revolution which prevents sagging of the rolls and which provides anniform distribution of stress on the rolls. Third, upon termination of the oscillation operation the articles assume the same positions they occupied at'the time oscillation .was initiated. Fourth, the actuator 66 is visible to the operator and provides a convenient visual indication of the positions of `articles being oscillated.

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications are possible and it is desired to cover all modifications falling within the spirit andscope of the invention.

What we claim as new and desire to secure by Letters vPatent of the United States is: i

1. A roller hearth furnace comprising in combination; an elongated structure including a furnace section for heating articles, Y a plurality of spaced parallel rotatable rolls having axes yextending transverse to the length of said structure for supporting said articles, drive means'for rotating said rolls about' their axes to convey said articles through vsaid furnace section, said drive means including a reversible electric motor which when rotated in one direction effects rotation of said rolls in one direction Yand which when rotated in the opposite direction effects rotation of said rolls in the opposite direction, first control means for controlling the direction of rotation of said motor, said first control means including switch means actuatable to a first position for effecting rotation of said motor in one direction and actuatable to a second position for effecting rotation of said motor in the opposite direction, switch actuating means :adapted for selective connection to one of said rolls for rotation therewith to actuatesaid switch means to said first and second positions in alternation each time said one roll rotates substantially a complete revolution, and

second control means including clutch means for controlling connection of said switch actuating means to said one of said rolls.

2. A furnace as defined in claim 1 wherein said switch actuating means comprises a pointer which extends substantially perpendicular to the axis of said one roll, said switch means including a switch operating lever which is spring biased to a central neutral position in the path of rotation of said pointer, and including a pair of normally open switches which are selectively closed when said switch operating lever is moved in either direction a predetermined distance away from its central neutral position.

3. A furnace as defined in claim 1 wherein said switch actuating means comprises a pointer which extends substantially perpendicular to the axis of said one roll, said clutch means comprising a cylindrical hub fixedly receiving a part of said one roll and having an annular flange intermediate its ends, a magnetic armature secured to said pointer surrounding said hub on one side of said annular flange, a stationary coil surrounding said hub on the other side of said annular flange, and bearing means permitting rotation of said hub relative to said armature and said pointer and also relative to said coil when said coil is deenergized, said coil when energized producing a magnetic field which attracts said armature and said pointer to said annular flange whereby said pointer and hub rotate as a unit.

4. A furnace as defined in claim 1 wherein said second control means includes limit switch means actuatable in response to arrival of an article at a predetermined location on said rolls for effecting operation of said clutch means to connect said switch actuating means to said one roll.

`5. A furnace as defined in claim 1 wherein said second control means includes a manually actuatable switch effective when actuated to operate said clutch means to connect said switch actuating means to said one roll.

6. A roller hearth furnace comprising in combination;

a furnace section for heating articles,

an exit section adjacent said furnace section for receiving heated articles from said furnace section,

a plurality of spaced parallel rotatable rolls in said furnace section having axes extending transverse to said furnace section for supporting said articles,

drive means for rotating said rolls about their axes to convey said articles through said furnace section to said exit section, said drive means including a reversible electric motor which when rotated in one direction effects rotation of said rolls in one direction and which when rotated in the opposite direction effects rotation of said rolls in the opposite direction,

control means operable for controlling the direction of rotation of said motor, said control means being effective when operated to reverse the direction of rotation of said motor each time one of said rolls rotates through approximately a complete revolution to thereby oscillate said rolls and articles supported thereon, and

sensing means operable in response to arrival of an article at a predetermined location in said furnace section while an article is in said exit section for operating said control means whereby articles in said furnace section are oscillated back and forth for preventing their conveyance to said exit section while an article remains in said axit section.

7. A furnace as defined in claim 6 wherein said control means includes switch means, switch actuating means adapted for selective connection to one of said rolls for rotation therewith to actuate said switch means, and clutch means operable in response to operation of said sensing means to connect said switch actutaing means to said one roll.

8. A furnace as defined in claim 6 wherein said sensing means includes a first normally open limit switch which is closed in response to arrival of an article at said predetermined location in said furnace section, a second normally open limit switch which is' closed in response to arrival of an article at said exit section from said furnace section, and relay means operable when both said first and second limit switches are closed for operating said control means.

9. A furnace as defined in claim 6 including a manually actuatable switch effective when actuated to operate said control means independently of said sensing means.

10. A furnace as defined in claim `6 including a door between said furnace and exit sections, door control means operable to open said door in response to arrival of an article at said predetermined location in the furnace section in the absence of an article in said exit section, and means including said sensing means for rendering said door control means ineffective to open said door when an article is in said exit section.

11. A furnace as defined in claim 6 including alarm means operable to provide an alarm indication, and alarm control means responsive to operation of said sensing means for operating said alarm means.

12. A furnace as defined in claim 7 wherein said switch actuating means comprises a pointer extending substantially perpendicular to the axis of said one roll and in depending relation to said axis when said pointer is disconnected from said one roll, said switch means includ- 15 ing a switch operating lever which is spring biased to a normally vertical neutral position in the path of rotation of said pointer, and a pair of normally open switches which are selectively closed when said lever is moved in either direction a predetermined distance away from its neutral position.

13. A roller hearth furnace comprising in combination:

a furnace section for heating articles,

an exit section adjacent said furnace section for receiving heated articles from said furnace section,

a door intermediate said furnace and exit sections,

a plurality of spaced parallel rotatable rst rolls having axes extending transversely to said furnace section for supporting articles in said furnace section,

a plurality of spaced parallel rotatable second rolls having axes extending transverse to said exit section for supporting articles in said exit section,

first drive means for rotating said irst rolls about their axes to convey articles through said furnace section, said first drive means including a reversible electric irst motor which when rotated in one direction effects rotation of said first rolls in one direction and which when rotated in the opposite direction effects rotation of said rolls in the opposite direction,

second drive means for rotating said second rolls about their axes to convey heated articles along said exit section, said second drive means including an electric second motor,

a first switch actuatable in response to arrival of an article at a predetermined location in said furnace section adjacent said door,

a second switch actuatable in response to arrival of an article at said exit section from said furnace section,

first control means operable in response to actuation of said first switch while said second switch is unactuated to open said door and start said second motor to move an article from said furnace section through said open door to said exit section, and

second control means operable when both first and second switches are actuated for rendering said first control means inetfective and for periodically reversing the direction of rotation of said Ifirst motor to thereby eifect oscillation of articles within said furnace section back and forth until removal of an article from said exit section causing actuation of said second switch.

14. A furnace as defined in claim 13 wherein said second control means includes switch means for controlling the direction of rotation of said first motor, switch actuating means adapted for selective connection'to one of said rolls for rotation therewith to actuate said switch means, and clutch means operable to connect said switch actuating means to said one roll.

15. A furnace as defined in claim 13 including alarm means operable to provide an alarm indication, and alarm control means responsive to operation of said second control means for operating said alarm means.

16. A furnace as defined in claim 13 including a manually actuatable switch effective when actuated to periodically reverse the direction of rotation of said rst motor independently of said first and second switches.

17. A furnace as defined in claim 14 wherein said switch actuating means comprises a pointer extending substantially perpendicular to the axis of said one roll and in depending relation to said one roll when said pointer is disconnected from said one roll, said switch means including a switch operating lever which is spring biased to a normally vertical neutral position in the path of rotation of said pointer, and a pair of normally open switches which are selectively closed when said lever is moved in either direction a predetermined distance away from its neutral position.

References Cited UNITED STATES PATENTS 1,969,708 8/1934 Beeke 263-60 2,167,922 8/ 1939 Witting et al. 263-6C JOHN J. CAMBY, Primary Examiner 

